This invention relates to an optical disk drive.
Generally, an optical disk drive is arranged to write and read data on an optical disk by means of a laser beam. The optical disk drive includes a light source module that emits the laser beam and an optical head carrying an objective lens that converges the laser beam on a small light spot on the optical disk.
The tracking operation of the optical disk drive includes (1) a rough tracking operation and (2) a fine tracking operation. The rough tracking operation is accomplished by moving the optical head crossing the tracks of the optical disk. The fine tracking operation is accomplished by minutely moving the light spot on the optical disk. For this purpose, a galvano mirror is provided in a light path between the light source module and the objective lens. When the galvano mirror is swung by a certain degree, the angle of incidence of the laser beam incident on the objective lens is changed, so that the light spot on the optical disk is moved.
Generally, a galvano mirror is mounted to a swingable mirror holder. Coils are provided to opposing ends of the mirror holder. Magnets are provided to a stationary part of the optical head so that the magnets are faced with the coils. The galvano mirror is swung by an electromagnetic induction caused by current flow in the coils and a magnetic field caused by the magnets.
In order to swingably support the mirror holder, it is necessary to provide a pivoting mechanism such as pivoting shafts and bearings. However, if such a pivoting mechanism is provided to the mirror holder, it may increase the size of a galvano mirror unit (including the galvano mirror, the mirror holder and the pivoting mechanism), particularly in the direction of a swinging axis of the galvano mirror. Thus, it is desired to provide a simple arrangement for swingably supporting the galvano mirror.
Further, in order to connect the coils of the mirror holder to a control circuit (provided on the stationary part), wires are laid between the mirror holder and the control circuit. Accordingly, when the galvano mirror is swung, the wires also move and may disturb the swinging of the galvano mirror. Thus, it is desired to provide an electrical feeding path which does not disturb the swinging of a galvano mirror.
It is therefore an object of the present invention to provide a galvano mirror unit in which a galvano mirror is supported in a simple manner.
Further, it is another object of the present invention to provide a galvano mirror unit in which an electrical feeding path does not disturb the swinging of a galvano mirror.
According to one aspect of the present invention, there is provided a galvano mirror unit including a galvano mirror, a mirror holder holding the galvano mirror, and a hinge member which swingably supports the mirror holder. The hinge member includes a support plate and a base. The support plate has a thinner portion extending across the support plate in one direction, so that the thinner portion divides the support plate into first and second sections. The first section is fixed to the mirror holder, while the second section is supported by the base. The mirror holder is swingable about the thinner portion, due to an elastic deformation of the thinner portion.
With such an arrangement, it, is not necessary to provide a pivoting mechanism such as pivoting shafts. Thus, the structure of the galvano mirror unit is simple, which is advantageous in miniaturization of the galvano mirror unit.
In a particular arrangement, the support plate has a rectangular-shape. The thinner portion is formed in the vicinity of one end of the support plate and is extended in parallel to the end.
In a preferred embodiment, when the thinner portion is not elastically deformed, the first and second sections are aligned on one plane. The plane is perpendicular to a mirror surface of the galvano mirror. Accordingly, the hinge member is able to resist against the force in the direction perpendicular to a mirror surface of the galvano mirror.
Advantageously, the mirror holder includes a mirror mounting portion to which the galvano mirror is mounted, and a recess in which the support plate is inserted. The recess is located to an opposing side to the mirror mounting portion. Since the support plate is inserted in the recess of the mirror holder, a space occupied by the hinge member is relatively small.
According to another aspect of the present invention, there is provided a galvano mirror holder having a mirror mounting portion to which the galvano mirror is mounted, a pair of coils provided to opposing ends of the mirror holder, and a hinge member which swingably supports the mirror holder. The hinge member is located at an opposing side to the mirror mounting portion of the mirror holder. With such an arrangement, the hinge member is able to resist against the force in the direction perpendicular to a mirror surface of the galvano mirror.
According to still another aspect of the present invention, there is provided a galvano mirror unit including a galvano mirror, a mirror holder holding the galvano mirror, a hinge member which swingably supports the mirror holder, a pair of coils provided at opposing ends of the mirror holder, and a pair of conductive members is provided in the hinge member. Electricity can be supplied to the coils via the conductive members.
With such an arrangement, it is not necessary to fix wires to the mirror holder. Thus, when the mirror holder swings, the swinging of the mirror holder is not disturbed by such wires.
In a particular arrangement, the conductive members respectively have contact surfaces which are exposed to an exterior of the hinge member. The mirror holder has mating surfaces which contact with the contact surfaces of the conductive members.